1. Field of the Invention
The present invention relates to load carrying vehicles, and more particularly, but not by way of limitation, relates to a method for transporting one semi-trailer and tractor combination upon a second semi-trailer and tractor combination, and further relates to a novel semi-trailer and tractor construction which can be transported in accordance with the method of the present invention.
2. Brief Description of the Prior Art
As is well known in the trucking industry, in order to obtain maximum utilization and therefore maximum efficiency and profit from the operation of a fleet of trucks, it is necessary to have a pay load at all times. Thus, on long trips, it is essential to carry one pay load during the out trip, and another pay load during the return trip. However, in practice, the pay load during the return trip is seldom available and the truck must be returned to its base of operation empty. This situation is especially prevalent when hauling steel beams and the like on flat bed trucks from a fabrication mill, or in hauling wheat from outlying elevators to a granary. Not only is the empty return trip uneconomical because of the use of fuel, but it also results in considerable wear on the vehicle. In this respect, it will be appreciated that the damage to the vehicle is compounded by the fact that the spring suspension system is designed to carry a heavy load. Therefore, when the truck is operated without a load, it is, for all practical purposes, rigidly supported rather than spring supported, which results in severe vibrations and shocks, especially to the semi-trailer. On trips of any substantial length, the driver usually must stay overnight and sleep before he is able to safely drive the return trip. This not only results in wasted operator time, but also greatly reduces the usable time of the truck.
In view of these fundamental difficulties in fully utilizing trucks, it has long been recognized that whenever the job is such as to require two trucks to carry a pay load to a destination, and there is no return load, it would be desirable to transport one truck by the other. Although this concept has occasionally been used to transport a smaller truck on a larger one, it heretofore has not been feasible because all trucks designed for long hauls are invariably constructed as large as possible and still remain within the maximum length, width and height limitations imposed by the laws of the several states. Consequently, all trucks are of approximately the same overall dimensions and one truck cannot normally be loaded onto the other in the absence of special equipment.